Evolutionary Significance of Reduced and Supernumerary Teeth in the Dentition

Abstract

Crown diameters in I¹ through M¹, except for I², were compared between den titions having conical or missing upper lateral incisors (Group C) and those having normal teeth (Group N), as well as between the latter and those having supernumerary mosiodentes (Group M). The purpose of this study is to find relationship of the tooth number anomaly to the normal characters as represented by crown diameters in the remaining teeth, and to give possible information in regard to the evolutionary significance of anomalies in tooth number, especially of the supernumerary teeth.
Employing statistical tests, it was clearly proved that the Group C had generally smaller teeth than the Group N, but the Group M showed almost no difference from the latter, though some exceptions were present for the upper second premolar in males. However this exception seems to be negligible if one realizes that this tooth is morphogenetically most unstable in the series of teeth examined here.
The fact that the teeth are significantly smaller in the Group C than in the Group N very likely shows parallel evolutionary trends of the reduction in the upper lateral incisors and the other teeth in the dentition.
On the contrary, insignificant difference in the tooth size between the Groups N and M seems to suggest that the supernumerary teeth, or at least the mesiodentes, have no evolutionary importance. This, in turn, might support the theory of accidental variation in tooth germs for the origin of the supernumerary teeth.